What was the Intel 8086 and why was it significant?

The 8086 (1978) was Intel's first 16-bit processor and the ancestor of every x86 chip — the start of a backwards-compatibility chain still unbroken today.

The 8086 mattered less for its raw power than for what was built on it. With about 29,000 transistors, a 16-bit data path, a 20-bit address bus (so 1 MB of addressable memory), and a 5–10 MHz clock, it was modest even by the standards of its day. But IBM chose its cheaper sibling for the IBM PC, and that decision turned the 8086's instruction set into an industry standard.

Every x86 processor since has stayed backwards-compatible with it: software from decades ago can still run, because each new chip only adds to the 8086's instruction set rather than breaking it. The whole "x86" name comes from the numbering of its descendants — 8086 → 80186 → 80286 → 80386 — all ending in "86."

Tip: the closely related 8088 had the identical instruction set but a cheaper 8-bit external data bus; it's the chip that actually shipped in the original 1981 IBM PC.

Go deeper:

• Intel 8086 (Wikipedia) — the full history of the 8086, root of the x86 lineage.